{
	name:"BaseLineShape",
	drawATip(step,ctx){
		let fp = step[0]
		let sp = step[1]
		let {x,y} = fp
		let s = Math.tan360(sp.y-y,sp.x-x)
		let e = 0
		let r = ctx.ratio
		let hrw = ctx.ratio*5

		let ta = e>s?(s+e)/2:Math.PI+(s+e)/2
		let angle = e>s?(e-s):2*Math.PI-(s-e)
		angle = (angle*180/Math.PI).toFixed(2)

		if(angle<10)return
		ctx.save()
		ctx.lineWidth=1
		ctx.lineDash=[2]
		this.linend([{x:x-hrw,y},{x:x+hrw,y}],ctx)
		ctx.beginPath()
		ctx.moveTo(x,y)
		ctx.arc(
			x,
			y,
			r,
			s,
			e
			)
		ctx.stroke()
		ctx.restore()

		ctx.save()
		ctx.fillStyle=ctx.strokeStyle
		ctx.translate(x,y)
		ctx.rotate(ta);
			ctx.save()
			ctx.textAlign="left"
			ctx.fontSize=10
			ctx.translate(r+10,0)
			let text = `${angle}°`
			ctx.fillText(text,0,0)	
			ctx.restore()
		ctx.restore()
	}
}